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query-profiler

Express

Express 4.18 and later, 5 included: CI runs it on 4.18.0, 5.0.0 and the newest. Your server’s code does not change: follow Setup to install the package, profile the Prisma client and add the preload. A complete app, Express 5 with an N+1 to find, is in examples/express.

The dev command

Section titled “The dev command”
{
  "scripts": {
    "dev": "tsx watch --import query-profiler/register src/server.ts",
    "start": "node dist/server.js"
  }
}

In plain JavaScript, node --watch --import query-profiler/register src/server.js. Other watchers are in Setup.

Before Express 4.18

Section titled “Before Express 4.18”

Its body parser loses the request’s async context: a route that reads a body runs outside its profile, and its queries land in a background profile instead. Update to 4.18 or later.

CORS

Section titled “CORS”

With the cors middleware, a page on another origin can read X-Debug-Token: the preload exposes it. If you set exposedHeaders, your list replaces it, so add the token there:

app.use(
  cors({ origin: "http://localhost:5173", exposedHeaders: ["X-Total-Count", "X-Debug-Token"] }),
);

In production no response carries it, so the extra name does nothing.